Every summer we are inundated with news media reports warning that ... otherwise healthy adults and children are walking around dehydrated, even that dehydration has reached epidemic proportions. Let's put these claims under scrutiny. I was a co-author of a paper back in 2007 in the BMJ on medical myths. The first myth was that people should drink at least eight 8-ounce glasses of water a day. The source of this myth [may be] a 1945 Food and Nutrition Board recommendation that said people need about 2.5 liters of water a day. The sentence that followed closely behind ... read, "Most of this quantity is contained in prepared foods." Water is present in fruits and vegetables. It's in juice, it's in beer, it's even in tea and coffee. Before anyone writes me to tell me that coffee is going to dehydrate you, research shows that's not true either. A significant number of advertisers and news media reports are trying to convince you otherwise. Bottled water sales continue to increase. More recent studies [continue] to declare huge numbers of children to be dehydrated. A 2012 study in the Annals of Nutrition and Metabolism [claimed] that almost two-thirds of French children weren't getting enough water. Another in the journal Public Health Nutrition [declared] that almost two-thirds of children in Los Angeles and New York City weren't getting enough water. The first study was funded by Nestl Waters; the second by Nestec, a Nestl subsidiary. There is no formal recommendation for a daily amount of water people need.